Lithium ion batteries are most generally used as power storage techniques for electrical autos as a result of Li-ion batteries have excessive power density, energy density, greater cell voltage, and low self-discharge as in comparison with lead acid batteries, NiCd batteries. The battery pack of an electrical automobile consists of a number of cells related in series-parallel mixture to realize the required energy requirement of the battery pack. The battery pack producer goals to offer excessive power density and security to its battery pack. These each options rely a lot on the shape issue (geometry) of the cell aside from chemistries concerned in manufacturing of cells. The primary type elements used for Li-ion batteries in EVs are Cylindrical, Prismatic, and Pouch.
The primary distinction between the cell codecs lies within the design of the cell casing and the association of the cathode, anode, and separators. Cylindrical and Prismatic cells are packaged in a tough case, often product of aluminum or chrome steel whereas Pouch cells are packed in multilayer aluminum composite foils. EV producers use all these cell codecs of their battery pack. For instance, Tesla makes use of cylindrical cells, and VW, BMW use prismatic cells whereas Nissan leaf makes use of pouch cells.
Cylindrical Cell
It’s the commonest Li-ion cell utilized in electrical autos. Cylindrical batteries primarily include a jelly roll together with anode, separator, cathode, and a cap positioned on the highest of the optimistic terminal. A security valve is offered to facilitate the discharge of gases which have accrued contained in the cell attributable to thermal runaway.
The Li-ion cell’s jellyroll construction provides it good mechanical stability, lengthy calendar life, and biking capability. Furthermore, cylindrical cells are simple to fabricate, are decrease value than different batteries, and might stand up to excessive inside pressures attributable to their metal case. Therefore, cylindrical cells are most well-liked for electrical autos. Cylindrical cells can be found in lots of codecs however essentially the most generally used codecs are 18650, 21700, and 4680.
Prismatic Cell
In this kind of cell, electrodes, lively supplies and different parts are organized in a prismatic or rectangular form. There are two frequent configurations for prismatic cells: flat jelly rolls and stacked electrodes.The flat jelly roll design is usually used to create a slim and rectangular type issue, appropriate for functions the place house effectivity is essential. And the Stacked electrode prismatic cells are identified for his or her capability to deal with greater power densities and supply improved cooling, which will be useful for high-performance functions.
Flat jelly rolls Prismatic Cell Stacked electrodes Prismatic Cell
Prismatic cells are often greater than cylindrical ones, which signifies that, compared, fewer cells are wanted to realize the identical power content material, and fewer electrical connections and time are vital, probably enabling a less expensive battery meeting course of. Prismatic cells present greater power density however much less energy density than cylindrical cells. Nevertheless, Prismatic cells are much less environment friendly in radiating warmth due greater dimension which causes thermal points with this cell. Additionally, Prismatic cells are made up of many optimistic and detrimental electrodes sandwiched collectively giving extra risk for deformation resulting in swelling and brief circuit.
Pouch Cell
That is one other format through which Li-ion batteries are packaged. Pouch cells are constructed by stacking a number of layered sheets of anode-separator-cathode assemblies that are then inserted right into a pouch, the pouch is then stuffed with electrolyte and sealed leaving the optimistic and detrimental terminals exterior of the pouch. The quilt of the pouch cell is product of aluminum and polyamide movie to forestall corrosion.
The elimination of the inflexible steel enclosure saves weight and means the pouch cell is able to excessive power densities and packing efficiencies. However this elimination within the pouch causes the Pouch cell to be weak to exterior mechanical harm and swelling from inside gasses. Pouch cells have greater floor space to quantity ratios than different codecs so pouch cells radiate warmth extra effectively.
A comparability desk for Cylindrical, Prismatic and Pouch Cells
PropertiesCylindricalPrismaticPouch Vitality Density
(pack degree)
LowExcessiveHighestMechanical StabilityHighestExcessiveLowThermal StabilityHighestLowExcessiveManufacturing ExpertiseMatureNonetheless creatingNonetheless creatingPriceLowExcessiveHighestBattery Pack WiringHighestLowLowWeightHighestExcessiveLow
In comparison with prismatic cells, cylindrical cells will be produced a lot sooner so extra KWh per cell will be produced day-after-day equaling decrease $ per KWh. The electrodes in a cylindrical cell are wound tightly and encased in a steel casing, This minimizes electrode materials from breaking apart from the mechanical vibrations, thermal biking from charging and discharging and mechanical growth of the present conductors inside from thermal biking. Many cells are mixed in collection and in parallel to extend voltage and capability of the battery pack, if one cell goes unhealthy, the influence on the complete pack is low. CHARGEX® cells bolt by way of lengthway circuit boards that may forestall a nasty cell from shorting out the remainder of the pack, permitting it to proceed functioning with barely diminished capability. With prismatic cells if one cell goes unhealthy it could compromise the entire battery pack. Cylindrical cells can even radiate warmth and management temperature higher than prismatic cells. Prismatic cells are made up of many optimistic and detrimental electrodes sandwiched collectively leaving extra risk for brief circuit and inconsistency. The upper capability makes it tough for the BMS to guard every cell from over charging and dissipating warmth. The bigger cell dimension minimizes the chance for automation resulting in a decrease diploma of consistency. The inner electrodes can simply develop and contract inflicting deformation which may result in a inside brief circuit and are extra vulnerable to swelling much like lead batteries.